Question

The solubility product of a salt having general formula $M{X}_2$ in water is $4\times {10}^{-12}$. The concentration of $M^{2+}$ ions in the aqueous solution of the salt is:

• A. $2.0\times {10}^{-6}M$
• B. $1.0\times {10}^{-4}M$
• C. $1.6\times {10}^{-4}M$
• D. $4.0\times {10}^{-10}M$

Answer 1

The correct option is B $1.0\times {10}^{-4}M$

Solubility product= $4\times {10}^{-12}$
$M{X}_2\rightleftharpoons \underset{s}{M^{+2}+}\underset{2s}{2X^{-}}$
If s is solubility, the solubility product
$K_{sp}=s\times (2s{)}^2$
$\Rightarrow K_{sp}=4s^3$
$\Rightarrow s=3\sqrt{\frac{K_{sp}}{4}}$
$\Rightarrow s=3\sqrt{\frac{4\times {10}^{-12}}{4}}$
$\Rightarrow s=1\times {10}^{-4}mol{L}^{-1}$